Polyphenylene ether resins comprise a class of thermoplastics which are characterized by outstanding physical properties, including hydrolytic stability, excellent dielectic properties, broad temperature use range and dimensional stability at elevated temperatures. They can be made by a variety of catalytic and non-catalytic processes from the corresponding phenols or reactive derivatives thereof. In general, they are prepared by the oxidative coupling of a phenolic compound with a complex metal catalyst. By way of illustration, descriptions of the preparation of polyphenylene ether resins are contained in Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875, and in Stamatoff, U.S. Pat. Nos. 3,257,357 and 3,357,358, which are incorporated herein by reference.
In the Hay patents, the polyphenylene ether resins are prepared by oxidative coupling comprising passing an oxygen-containing gas through a reaction solution of a phenol and a metal-amine complex catalyst. In the Stamatoff patents, the polyphenylene ethers are prepared by reacting the corresponding phenolate ion with an initiator, e.g., an acid peroxide, in the presence of a complexing agent.
The Cizek patent, U.S. Pat. No. 3,383,435, discloses compositions of polyphenylene ether resins and styrene resins. The thermoplastic compositions disclosed therein include rubber-modified styrene resins. Such compositions are important commercially because they provide improvement in the melt processability of the polyphenylene ether and improvements in the impact resistance of articles molded from the compositions, in addition to an upgrading of many other properties. The disclosure of the aforementioned Cizek patent is incorporated herein by reference.
Fillers are often included in these polyphenylene ether resin compositions for a variety of reasons, e.g., as reinforcers to increase stiffness, as well as to enhance other physical properties. Of special importance herein are filled polyphenylene ether/polystyrene compositions using titanate-type filler materials, such as potassium titanate whiskers. The presence of a filler in most cases, including titanate filled polyphenylene ether resin compositions, results in a decrease in toughness properties, i.e., impact strength and/or tensile elongation.
It has now been surprisingly discovered that the toughness of compositions of a polyphenylene ether, a polystyrene and a titanate filler can be improved by the presence of an adipic acid based polyester. The compositions of the invention, when molded, exhibit enhanced impact strength and tensile elongation in comaprison with titanate filled polyphenylene ether/polystyrene molding compositions without the polyester additive of the invention.